Treatment of fibrous cellulose for the production of hydrated derivatives



Patented mlune 1%, i?

CHARLES E. CROSS AND EDWARD J. BEVAN, OF LONDON, ENGLAND, ELIZA MARY'BIJAKE, EXECUTRIX OF SAID EDWARD J. BEVAN, DECEASED, ASSIGNORS TO I. P.M. SYNDICATE LIMITED, OF WESTMINSTER, LONDON, ENGLAND, A. BRITISHCORPORATION.

' TREATMENT OF FIBROUS CELLULOSE FOR THE PRODUCTION OF HYDRATED'DERIVATIVES.

lilo Drawing.

To all whom it may concern:

Be it known that we, CHARLES FREDERICK CRoss and EDWARD J; BEVAN, bothsubjects of the King of Great Britain, both residing in London, England,have jointly invented a certain new and useful Treatment of FibrousCellulose for the Production of Hydrated Derivatives, of which thefollowing is a specification.

The action of the alkaline hydrates in strong solution on fibrouscelluloses deteronines structural changes in the fibres, es-

pecially marked by shrinkage, and in the case of selected cotton textilefabrics the solutions of 12.5

action, with certain mechanical aids, is applied to produce theeffectsknown as mercerization. In practice the mercerizing process consists inapplying under the suitable conditions, an aqueous solution of causticsoda of 1517.5 per cent, (NaOH) at ordinary temperatures. The effectsare diminished as the concentration of the caustic soda is diminishedbelow 15 per cent; with er cent to 10.5 er cent .(NaOH) the diminutionof effect is rapid, and it may be said that at strengths below 12.5 percent caustic soda solution has no substantial mercerizing effect. Thuscotton or cotton fabric treated with an alkaline lye of 9 percentcaustic soda (NaOH) is not sensibly affected in the direction ofmercerization.

For the production of alkali-cellulose in the synthesis of water solublecellulose derivatives (by subsequent action of carbon disulphide) asdescribed in specification. of British Letters Patent No 8700 of 1892,it is 'known that the cellulose must be taken to the stage of fullmercerization and therefore the fibrous cellulose must be treated with asolution containing the equivalent of upwards of 15.0 per cent ofcaustic soda (NaOH). Alkali-celluloses for industrial production ofviscose, which implies com-- plete conversion to water solublederivatives in the subsequent reaction, are prepared by treating theair-dry cellulose with caustic soda lye of 17 per cent NaOH) strengthand pressing the product so that the fibrous Application filed April 26,1919. Serial No. 292,343.

(NaOH) in the proportion of twice the weight of the fibre or fabric, andthen exposed to, carbon disulphide, only a small fraction of "thematerial is converted into water soluble derivatives.

The attendant formation of water-insoluble xanthates is also fractionalin amount. But, as we have discovered, fundamental reaction occurs, andthe cellulose is profoundly modified. The new characteristics areevidenced in .further reaction with water; structural changes in thefibre are developed, with lar e increase of diameter, and thickening oft e cell wall, and in the mass thereare visible effects of hydration.The fibrous mass swells considerably, and retains a very much increasedpercentage of water, after having been pressed or centrifuged. Thefibres, however, though much distended remain free, and may be readilyand quickly washed free from excess of alkali, and the smallproportio-no-f soluble cellulose compounds. For subsequent removal ofresidual alkali and decomposition of fractional residues ofwater-insoluble xanthates, a treatment with dilute acid may bedesirable.

It is this fully hydrated condition of th cellulose and the impliedcorresponding plasticity of the substance, which gives rise to the noveltechnical results of the present invention, whichco-nsists in modifying.the cellulose for subsequent full hydration by treatment of thecellulose with alkali solution of a strength between 6 and 11 per cent(NaOH), and simultaneously or subsequently, with carbon disulphide.

As an example of the treatment, raw cotton fibre may be impregnated withtwice its weight of caustic soda, of 9 per cent strength and introducedinto a closed chamber together with carbon disulphide amounting to S y15 per cent of the weight of the original fibre. After a period of 610hours, at the ordinary temperature, the mass is transferred to. aconvenient apparatus, in which the product is now washed with water atordinary temperature for remoyal and recovery of alkali and to determineor develop the effects of hydration.

The structural modifications produced in the cotton fibreland thechanges accompanying the swelling of the fibre generally resemble thoseproduced-by saline solvents of cellulose in the earlier stages ofaction, that is mainly in the thickening by swelling of the cell wall. Amore special effect is the exaggeration of the central canal defined bysymmetrical sinuous out-lines. In extreme treatment a definitecontinuous spiral apaears in the massof'swollen fibre substance.

his development of the ultimate spiral differentations of the externaltissues of the cotton is more marked it the preparatory treatment withalkali is carried out at higher temperatures, say 80? to 90 C.

The hydration efi'ects are enhanced by increasing the proportion ofalkali to fibre in the first stage of treatment, for instance by usingan amount of caustic soda solution equal to 2.5 to 3.0 times the weightof the fibre. The effects may also be controlled by varying thetemperature of the alkali solution, the action of the latter indetermining hydration effects being greater the lower the temperature;on the other hand, raising the temperature alters the structuralcharacteristics of the hydrated product, and particularly in the sensethat when formed into a mass, or in sheets and subjected to pressure ityields a parchmentlike material.

The finally reverted air. dry product generally retains lO to 11 percent of moisture as compared with the 6 to 7 percent normal to the rawcotton fibre, which is correlative with a generally increased dyeingcapacity.

Instead of washing with water the material. which has been attacked bycarbon disulphide, it may be washed with a strong solution of a neutralalkali salt, for instance brine, to remove excess of alkali; thehydration effect is thus suspended and can be subsequently produced bytreatment with water. This brine treatment is useful in connection withthe recovery of the alkali,.which is thereby obtained in moreconcentrated state. as it is in furnishing a product which can besubsequently hydrated by Washing away the brine.

For the purposes of this invention the I term fibrous cellulose includes"the well- .known industrial forms at cellulose: cotton;

product, its use in paper-making has been '80 noted.

It is to be noted that the hydration effects give the necessarypapermaking quality, and are independent therefore of any hydrationetfects'such as produced in the ordinary Hollander or beater. alsofibrous cellulose of any length of fibre may be brought into the statenecessaryv for wet manipulation with conservation of length. Hence, finefelted sheets of say 15 grammes per sq. meter of area can be produced,showing considerable adhesion in the final reverted state.

The hydrated fibre in admixture with ordinary paper-making cellulose,that is, as a mixed fibre, produces its proportionate effect, and it ischaracteristic of the-rever sion that in the final form the fibreretains elasticity and bulk. I

In treating textile materials the process may be applied to roving, tobe afterwards spun and drawn by the wet process to yarn,

Therefore,-

Yarns and cloth may also be treated with I or without the tensionnecessary to oppose shrinkage of the material which occurs in thehydration process. I

In this way a range of finishes and effects are obtained with some ofthe characteristics of mercerization, but diflere'ntiated by reason ofthe relative elasticity and bulk of the fibre .or material in thefinished state.

Having thus'described the nature of the same invention and the bestmeans we know of" carrying the same into practical; effect, we claim 1.A process of treating fibrous cellulose which consists in subjecting thecellulose to the action of alkaline solution of strength between 6 and11 per cent (NaOH), and of carbon bisulphide at the ordinarytemperature.

2. A process of treating fibrous cellulose which consists in subjectingthe cellulose to the action of alkaline solution of strength between 6and 11. per cent (NaOH) and then to the action of carbon bisulphide atthe ordinary temperature.

1 3 A process of treating fibrous cellulose which consists in subjectingthe cellulose to the action of alkaline solution of strength I a between6 and 11 per cent (NaOH) and product with a strong solution of a neutralof carbon bisulphide at the ordinary temalkali salt. perature, andfinally washing the product 5. As a new product, hydrated fibrouscelwith a strong solution of a neutral alkali lulose having a thickenedcell wall and an 1 salt. exaggerated central canal defined by sym- 4. Aprocess of treating fibrous cellulose metrical sinuous outlines. whichconsists in subjecting the cellulose In testimony whereof we have signedour to the action of alkaline solution of strength names to thisspecification. between 6 and 11 per cent (NaOH) and then 1 to the actionof carbon bisulphide at the or- CHARLES F. CROSS. dinary temperature,and finally washing the EDWARD J. BEVAN.

